1. Field of the Invention
The present invention relates to a context aware system using sensors of varying availability, whereby the availability of sensors is managed external to the context aware system.
2. Description of the Related Art
Context awareness is a key technology for the next generation of smart devices. These devices will have a broad knowledge about what a user's desires and needs are and will act accordingly. This is achieved by utilising a multitude of internal and external sensors for collecting enough information to derive a reliable context information like for instance the position of a user or of person he is interested in, the identity of users currently using a device, and the kind of devices available for a user.
The term “context” as used in this specification is defined by Anind K. Dey in “Understanding And Using Context, Personal Ubiquitous Computing Journal, Volume 5 (1), 2001, pp. 4-7”, as any information that can be used to characterise the situation of an entity. An entity is hereby defined as a person, a place or an object that is considered relevant to an interaction between a user and an application, including the user and the applications themselves.
Knowledge about a context can be used in various ways to make application devices much smarter by automatically incorporating the context information. Context is usually a very complex matter resulting from the multiplicity of different types of context potentially derived from numerous different sensors. A tourist for example moving around a foreign city is supplied by her or his context aware device with an active map, and additionally with information about the sights she or he is currently viewing. A context aware device will hereto need—among others—information about the current location of the tourist. For the tourist being outdoor, this information can be obtained by using a global positioning system (GPS) but indoors, this is no longer feasible, because accessing GPS satellites is most of the time impossible within buildings. Therefore, special indoor location systems have to be used to retrieve the position information indoors. Whenever a user moves in or out of a building, his or her context aware device has to switch to another location defining system. Handling this takeover from the outdoor to the indoor location defining system and vice versa is currently performed on the application side, which works quite well when there are only a few possible sources of information available.
In some tactical military applications a sensor management system is deployed, like e.g. in tactical air fighters where it is used to reduce the workload of a pilot by controlling the sensors and allocating limited sensor resources to effectively detect, classify and track targets. The system supports the pilot by hiding the complexity of the on-board sensory by aggregating the available sensors and presenting only high-level data to the pilot. The system allows to dynamically plug in any kind of known sensor and utilise it immediately by the sensor management system. But it only works with sensors already known to the system, since there is also a need to implement the processing of the provided sensor data. Respective sensor systems are centralised and tightly coupled to the sensors.
Decentralised structures are provided by sensor networks which consist of a large number of possibly different sensors that interact together to exchange and propagate sensor data. Respective systems require no sensor management as not lookup of a specific sensor is done. Instead a request for a certain information is injected into the system and the results will be aggregated and returned to the calling instance without having any knowledge on where and how the data is created, which means that there is no management of aspects like finding and utilising the proper sensor.
For a context-aware system requiring a large number of sensors to retrieve the necessary data for obtaining the required type of information, a supervision of the availability and adequacy of the sensors is impracticable as it overburdens the system.
A tourist of the above example might for instance not only be interested in his own position, but also wants to know if certain persons move in or out a certain area, i.e. he wants to know for instance if his children are going too far away. A context system will hereto have to utilise a large number of location sensors of different types—indoor as well as outdoor—whereby the indoor location type might also differ from building to building and thus possibly from person to person to be discovered.
This is achieved by a system providing context information on request as described in the European patent application EP 1 298 527 A1 which uses an automatic set-up of a dynamic context graph configuration for providing a path from a request of context information to a context source available and suited to provide such information. A context source hereby represents the abstraction of a sensor towards the context system. The context sources are managed by the context graph's mechanism for enabling the construction of the required context information. Although the context graph configuration means is adapted to dynamically aggregate data from various context sources into high-level context information, it is not adapted and would be overburdened to search and utilise sensors supplying a context source.